This invention relates to techniques for converting crude ethanol or the like to lower ethyl isoalkyl ethers. In particular, this invention relates to an integrated system for converting crude ethanol to valuable products by etherifying lower branched olefins, such as C.sub.4 -C.sub.5 isoolefins. It is known that isobutylene may be reacted with ethanol over an acidic catalyst to provide ethyl tertiary butyl ether (ETBE) and isoamylenes may be reacted with methanol over an acidic catalyst to produce tertiary-amyl ethyl ether (ETAE). Those ethers having the formula C.sub.2 H.sub.5 --O--R, where R is an isoalkyl radical, are particularly useful as octane improvers for liquid fuels, especially gasoline.
Increasing demand for high octane gasolines blended with lower aliphatic alkyl ethers as octane boosters and supplementary fuels has created a significant demand for tertiary alkylethers, including the C.sub.6 and C.sub.7 ethyl alkyl ethers, such as ethyl tertiary-butyl ether (ETBE) or ethyl t-amyl ether (ETAE). ETBE and ETAE are known to be high octane ethers. An article by H. E. Buc et al., S. A. E. Journal (Transactions), Vol. 39, No. 3, p. 333, discusses the advantages one can achieve by using such material to enhance gasoline octane.
Ethanol may be readily obtained from biomass by fermentation in a known manner. Crude ethanol from such processes usually contains a significant, typically from minor amount of water, amounts up to 90 wt %. Large amounts of water are not generally desirable in etherification due mainly to hydration of olefins.
It is main object of the present invention to provide a novel and economic technique for removing excess water from crude ethanol feedstocks, including novel operating methods and equipment for treating the oxygenate feedstocks prior to etherification.